Although senior CIA officials in Bangkok were nominally in charge, they deferred to Mitchell, according to several sources familiar with events at the prison.

"There was a big sense of arrogance about him," one source said.

After Abu Zubaida was discharged, the FBI was shut out of the interrogations as Mitchell began establishing the conditions for Abu Zubaida's interrogation -- "creating the atmosphere," as he put it to colleagues.

In the initial stages, Abu Zubaida was stripped of his clothes while CIA officers took turns at low-intensity questioning. Later, Mitchell added sleep deprivation and a constant bombardment of loud music, including tracks by the Red Hot Chili Peppers. After each escalation, he would dispatch an interrogator into Abu Zubaida's cell to issue a single demand: "Tell me what I want to know."

Mitchell sometimes spoke directly to the prisoner, but unlike the CIA officers, he wore a mask, according to two sources familiar with the events in Thailand.

He repeatedly sought authorization from the CIA's Counterterrorist Center for his actions.

"The program was fully put together, vetted and run by the counterterrorism folks at the agency," the former U.S. official said. "CIA headquarters was involved directly in every detail of interrogation. Permission had to be obtained before every technique was used, and the dialogue was very heavy. There were cables and also an IM system. All Mitchell's communications were with the Counterterrorist Center."

In Bangkok, word circulated among those at the secret site that the tactics had been approved "downtown" -- agency jargon for the White House.

Escalating Torment

Soufan testified to Congress in May that Abu Zubaida went silent once Mitchell took charge. Within days of the CIA team's arrival, the cables between Bangkok and Langley became devoid of new revelations. Agency officials decided to let the FBI back into the interrogations, but on the condition that forced nudity and sleep deprivation be allowed to continue.

The CIA team lowered the temperature in Abu Zubaida's cell until the detainee turned blue. The FBI turned it back up, setting off a clash over tactics.

Under FBI questioning, Abu Zubaida identified an operative he knew as Abdullah al-Mujahir, the alias, he said, of an American citizen with a Latino name. An investigation involving multiple agencies identified the suspect as Jose Padilla, the al-Qaeda operative later convicted of providing material support for terrorism.

"In two different bits, after sleep deprivation, is when Abu Zubaida gave clues about who Padilla might be," the former U.S. official said. "When that was put together with other CIA sources, they were able to identify who he was. . . . The cables will not show that the FBI just asked friendly questions and got information about Padilla."